Methods of preparing holograms

ABSTRACT

Methods of producing holograms to be used in the SYSTEM AND APPARATUS FOR THE RECORDING AND PROJECTION OF IMAGES IN SUBSTANTIALLY 3-DIMENSIONAL FORMAT that is the subject of U.S. Pat. No. 6,224,562.

CROSS REFERENCE TO RELATED APPLICATION(S)/CLAIM OF PRIORITY

[0001] This application is a continuation-in-part of and claims benefitof co-pending U.S. Nonprovisional application Ser. No. 09/749,984 filedDec. 27, 2000, which in turn is a continuation of U.S. Nonprovisionalapplication Ser. No. 09/111,990 filed Jul. 8, 1998, now issued as U.S.Pat. No. 6,229,562, which in turn claims benefit of U.S. ProvisionalApplication Ser. No. 60/051,972 filed Jul. 8, 1997. The aforementionedpatent applications and patent are hereby incorporated by reference intheir entirety herein.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] Not applicable.

REFERENCE OF AN APPENDIX

[0003] Not applicable.

BACKGROUND

[0004] 1. Field of the Invention

[0005] This invention relates to methods of preparing holograms to beused in a SYSTEM AND APPARATUS FOR THE RECORDING AND PROJECTION OFIMAGES IN SUBSTANTIALLY 3-DIMENSIONAL FORMAT.

[0006] 2. Brief Description of Related Art

[0007] U.S. Pat. No. 6,229,562, that is incorporated herein by reference(hereinafter referred to as “patent '562”) discloses and claims a SYSTEMAND APPARATUS FOR THE RECORDING AND PROJECTION OF IMAGES INSUBSTANTIALLY 3-DIMENSIONAL FORMAT. The invention described thereinderives from the principles of holography and/or integral photography.Patent '562 first discloses a basic principle of magnification andprojection. This principle permits magnification and projection of3-dimensional images uniformly in all directions, thereby overcomingdrawbacks in the prior art. Based upon this principle, cameras aredescribed, in their various embodiments, that photograph a scene andretain the 3-dimensional information therein. An editor is alsodescribed that would edit integral photographs and holograms containingthe 3-dimensional information from the photographed scene. In addition,a theater is designed to project the magnified 3-dimensional scene thatwas photographed, upon a large screen to be viewed by an audience.Further, the projectors and screens are described in their variousembodiments.

[0008] Within some of the embodiments of the camera and projector,specially prepared holograms are used as optical elements therein. Useof these holograms affords the advantage of being able to replacecomplex, bulky, difficult to manufacture, and expensive conventionaloptical elements needed to produce certain types of images duringphotography, magnification, and projection. In addition, some of theembodiments of the screen are themselves holograms. Unlike conventionalprojection screens used in current theaters, the screen described inpatent '562 is an active optical element that, when combined with theprojection optics, causes light waves to emanate from the screen intothe theater that are the same as though the 3-dimensional scene werereal. Therefore, the viewing audience should not be able to perform anyvisual test to determine whether or not the projected 3-dimensionalscene truly exists. The use of a specially developed holographic screenaffords the advantage of replacing more conventional optical componentsused in screen fabrication.

[0009] In view of the above, it is therefore an object of the inventionto provide methods of preparing the various holograms used as opticalelements in the camera, projector, and screen embodiments described inpatent '562.

SUMMARY OF THE INVENTION

[0010] The object of the invention as well as other objects which shallbe hereinafter apparent are achieved by the METHODS OF PREPARINGHOLOGRAMS comprising methods of producing the various holographicoptical elements specified and claimed in patent '562.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The invention will be better understood by the DetailedDescription of the Preferred and Alternate Embodiments with reference tothe drawings, in which:

[0012]FIG. 1 illustrates the method of magnification that is the basisfor both this application and patent '562.

[0013]FIG. 2 illustrates how a magnified image can be projected beforean audience.

[0014]FIG. 3 is a schematic of primary holographic projection using twomatrix lens arrays.

[0015]FIG. 4 is a schematic showing the optics of the preferredembodiment of the holographic projector.

[0016]FIG. 5 illustrates how HOLOGRAM #1 in FIG. 4 can be prepared.

[0017]FIG. 6 illustrates how HOLOGRAM #2 in FIG. 4 can be prepared.

[0018]FIG. 7 is a schematic showing the standard method of imageinversion.

[0019]FIG. 8 shows how image inversion can be accomplished without lossof resolution.

[0020]FIG. 9 is a schematic of holographic multiplexing optics.

[0021]FIG. 10 is a schematic showing the method of holographicmultiplexing using the optics shown in FIG. 9.

[0022]FIG. 11 shows the process for formation or manufacture of thefront projection holographic screen.

[0023]FIG. 12 shows the method of reconstruction from projection ontothe front projection holographic screen.

[0024]FIG. 13 is a schematic of a primary holographic imaging systemusing high quality optics.

[0025]FIG. 14 shows the method of fabricating a high quality holographicimaging system.

[0026]FIG. 15 shows how the holographic imaging system of produced usingthe method of FIG. 14 can be used for projection of high quality images.

[0027]FIG. 16 shows the use of a hologram whose reconstructed real imageis a 2-dimensional integral photograph.

[0028]FIG. 17 shows a method of preparing strip holograms.

[0029]FIG. 18 shows image inversion from pseudoscopy to orthoscopy usingintegral photography.

[0030]FIG. 19 shows image inversion from pseudoscopy to orthoscopy usingholography and integral photography.

[0031]FIG. 20 shows image inversion from pseudoscopy to orthoscopy usingholography.

DETAILED DESCRIPTION OF THE PREFERRED AND ALTERNATE EMBODIMENTS

[0032] The present invention, in all its embodiments, is based upon amethod that permits magnification of a 3-dimensional image produced froma photograph, hologram, optical system or other system or device,regardless of the medium or the method, in such manner as to preservethe depth to height and width relationship of the image as it existedprior to magnification. This method requires the 3-dimensional imageprior to magnification to be rendered as an array of 2-dimensionalimages by some form of matrix lens array, such as a fly's eye lens. Werethis array of 2-dimensional images to be magnified by some magnificationfactor, and then viewed or projected through a new matrix lens arraythat has been scaled up from the lens array that produced the originalarray of 2-dimensional images, such that the scaling factor is equal tothe magnification (i.e., the focal length and diameter of each lensletmust be multiplied by the same magnification factor), a new3-dimensional image would be produced that would be magnified by thesame magnification factor, and all image dimensions would be magnifiedby the same factor such that all dimensions of the final 3-dimensionalimage would be proportional to the dimensions of the original image. Theutility of magnifying 3-dimensional images using this method would bethe ability to enlarge holograms or integral photographs or other mediafrom which 3-dimensional images are produced, or to project still ormoving 3-dimensional images before a large audience.

[0033] The magnification principle is illustrated in FIG. 1. Object 1 isphotographed by matrix lens array 2, thereby producing integralphotograph 3. Integral photograph 3 is then magnified to give integralphotograph 4 which is then placed behind matrix lens array 5. Thiscombination yields magnified image 6. It must be noted here, that duringscaling-up, the (F/#) of the lenslets remains constant.

[0034] Projection is merely another form of magnification. The onlydifference lies in the fact that no permanent record is produced as inphotography. To illustrate the principle of projection, let us use as anexample, the technique of rear projection shown in FIG. 2. (As will beseen later, it is also possible to illustrate this principle with frontprojection.) Were an integral photographic transparency to be projectedat some given magnification onto a translucent screen 7 which is behinda large matrix lens array 8, an observer 9 in the audience sitting infront of the matrix lens array will see the magnified 3-dimensionalimage 10. The 3-dimensional image can be made orthoscopic, and can bemade to appear either in front of or behind the matrix lens array.

[0035] The camera consists of an optical system that would produce the2-dimensional array of 2-dimensional images on a plane, the plane and/orrecording medium whereon the 2-dimensional array is produced, themechanical apparatus (if any) associated with the image plane and/orrecording medium, a means (if any) for adjusting the optical system forfocus and/or special effects, and the housing (if any) that integratesthe optical system, the mechanical system and the image plane and/orrecording medium into a single unit. An example of the optical system isa matrix lens array such as a fly's eye lens arranged so as to produce arectangular matrix array of rectangular 2-dimensional images. The imageplane, for example, would contain a film for recording the 2-dimensionalimages. Once developed, the matrix array photograph would be called anintegral photograph. If the camera is a motion picture camera capable ofcapturing moving 3-dimensional images in the form of a sequential seriesof integral photographs, a film motion and film stabilization mechanismwould be required. Finally, such a camera might require a housing tointegrate the components and to provide a dark environment so as to notexpose the film unnecessarily.

[0036] The projector consists of an optical system that would project amagnified image of the processed 2-dimensional integral photographproduced by the camera onto an image plane that would be converted bythe screen into a magnified 3-dimensional image, the mechanicalapparatus (if any) associated with the image plane and/or recordingmedium, a means (if any) for adjusting the optical system for focusand/or special effects, and the housing (if any) that integrates theoptical system, the mechanical system and the image plane and/orrecording medium into a single unit. If the projector is a motionpicture projector capable of magnifying moving 3-dimensional images inthe form of a sequential series of integral photographs, a film motionand film stabilization mechanism would be required. Finally, such aprojector might require a housing to integrate the components and aprojection lamp.

[0037] The screen consists of an active optical system configured as amatrix lens array comprised of a plurality of optical elements. Thescreen has the same number of active optical elements as the matrix lensarray used in the camera and configured identically as in the camera. Inthe preferred embodiment of the system, the matrix lens array of thescreen is larger than that of the camera such that the ratio of thediameter of the screen lenslets to the diameter of the camera lensletsis equal to the image magnification. However, the (F/#) of the lensletsin the screen matrix lens array must be equal to the (F/#) of thelenslets in the camera matrix lens array. Finally, the screen mightconsist of a mechanism to filter the color of certain portions of theprojected image in order to produce a color rendition of a sceneprojected upon it in black-and-white.

[0038] Patent '562 describes a number of methods for projecting thephotographed scene residing on a 2-dimensional integral photograph orhologram onto a large screen thereby creating a magnified 3-dimensionalimage of the scene. Many of these utilize complex systems comprised ofconventional optics. Conventional optical systems such as thosedescribed in patent '562 are expensive to manufacture, and the imagesproduced therefrom are subject to abberation and distortion. Bycontrast, holographic imaging devices are inexpensive to manufacture,and images produced from them are generally abberation and distortionfree. One method of accomplishing projection using a holographic imagingdevice is shown in FIG. 3. This is the preferred embodiment of theprojection system. In this case, instead of using expensive projectionlenses, two matrix lens arrays, 11 and 12, are used as shown. On thesecondary image plane 14, the image is magnified by the desired amount,and the ratio of the size of the elements of matrix lens array 12 tomatrix lens array 11 is equal to the magnification. The hologram isprepared as follows. In the setup shown in FIG. 3, replace both the film13 and the secondary image plane 14 by two diffuser plates. Between thefilm plane diffuser plate and matrix lens array 11, place a movableaperture which is the size of one element on the film frame 13, andbetween the secondary image plane and matrix lens array 12, place asimilar movable aperture which is the size of a magnified element on thesecondary image plane 14. A high resolution photographic plate ispositioned in the hologram plane 15. The film plane aperture is placedin front of the first elemental position and the secondary image planeaperture is placed in the corresponding first elemental position. Bothdiffuser plates, 13 and 14, are then trans-illuminated by an appropriatelaser for a sufficient time to expose the hologram 15. (This may have tobe done for each element by exposing it with many bursts of lowintensity laser radiation.) Both apertures are then moved to the secondelemental positions and the hologram is exposed again; and so-on forevery elemental position. Another method of preparing the same hologramis to also place an appropriate elemental aperture in front of thehologram plane 15. This elemental aperture moves to a different positionin front of the hologram plane every time the other two apertures move.The addition of this third aperture will avoid reciprocity problems withthe photographic emulsion. (Reciprocity problems will also be avoided bythe short-burst method mentioned above. The advantage of the short-burstmethod over the third aperture method is that crosstalk between elementsis avoided.) This method of projection using holographic imaging seemsto be the most practical embodiment of the projection principle.

[0039] Holographic imaging devices can be used with more-or-lessstandard, inexpensive lenses to accomplish all projection functions.FIG. 4 shows the final schematic configuration of this type ofprojector. This represents the preferred embodiment of the optics of theholographic projector. The image on the film 16 is first magnified ontoa secondary image plane 17 holographically using two matrix lens arrays,18 and 19, and the first hologram 20. This magnified image is then usedas the reference beam for the second hologram 21 so as to reconstruct amagnified, unmultiplexed, inverted image on the unscrambled image plane22. This unscrambled image plane can either be an intermediate plane orthe screen itself. In the configuration shown, it is an intermediateplane, and a position adjustable projection lens 23 is used to projectthe image formed at this plane onto the screen. No diffuser plates areneeded at the intermediate image planes (although they can be used ifnecessity dictates), and their use is undesirable since they add greatlyto the required illumination levels. The first and second holograms, 20and 21, are shown in the figure as volume or reflection holograms.Transmission holograms can also be used, but the efficiency oftransmission holograms is less than reflection holograms. Therefore,using transmission holograms would also add to the required illuminationlevels. The only non-holographic optical elements in the projector areeither simple projection lenses or matrix lens arrays. Therefore, theholographic projector represents a far simpler system than the projectorusing more conventional optics.

[0040]FIG. 5 illustrates how the first hologram 20 in FIG. 4 can beproduced. Two active optical systems are used to produce the referenceand object beams necessary to expose the photographic plate to producethe reflection hologram. The first active optical system is comprised ofa diffuser plate 24 and the first matrix lens array 25. When illuminatedby coherent light, the diffuser plate 24 scatters the light which isstill coherent, and the scattered light impinges upon the matrix lensarray 25 which, in turn, produces the reference beam 26. The secondactive optical system is comprised of a diffuser plate 27 and the secondmatrix lens array 28. When illuminated by coherent light coming from thesame source as that which illuminated the first active optical system,the diffuser plate 27 scatters the light which is still coherent, andthe scattered light impinges upon the matrix lens array 28 which, inturn produces the object beam 29. The reference beam 26 and the objectbeam 29 impinge upon opposite sides of the unexposed transparentphotographic plate 30. This photographic plate, when developed andprocessed, becomes the first hologram 20 of FIG. 4. It should be notedthat, with a hologram of this type, it is possible, and it might bedesirable to eliminate the second matrix lens array 19 from theprojection optics of FIG. 4, while producing the same result.

[0041]FIG. 3 shows a optical system consisting of more than onehologram. Holograms can be used as imaging devices in the camera as wellas in the projector. One of the tasks of holographic optical systems isto perform multiplexing and unmultiplexing. Multiplexing is the processof optically compressing the elemental images of an integral photographand then scrambling their relative positions so as to enable them to fitinto a small space on the image plane. In a camera, the image planewould normally contain photographic film, but the medium could besomething else such as image orthocon tubes. Unmultiplexing is thereverse process of expansion and unscrambling the images from themultiplexed image plane and projecting it onto a second image plane sothat the image becomes a readable integral photograph. Multiplexing mustbe performed by the camera while unmultiplexing must be performed by theprojector.

[0042] Another task that can be performed by a holographic opticalsystem is the conversion of the final 3-dimensional image frompseudoscopy to orthoscopy. A viewing audience expects to see anorthoscopic 3-dimensional image of a scene. Orthoscopy occurs normallywhere a first object that is supposed to be in front of a second objectappears closer to the viewer. Pseudoscopy occurs where the second objectappears closer to the viewer. This is an unnatural viewing conditionthat would be annoying to an audience. Unfortunately, the image producedusing the basic principle of magnification and projection ispseudoscopic. Therefore, optics must be used to convert from pseudoscopyto orthoscopy.

[0043] In patent '562, the most practical method and the preferredembodiment of unmultiplexing is with the use of a holographic imagingdevice. Not only can the entire image unmultiplexing process beaccomplished in one step using such an element, but so also can both theinversion of the image from pseudoscopy to orthoscopy and the finalprojection (if these steps are desired to be performed using thismethod). The use of this method is shown in FIG. 6. The magnified imagefrom the secondary image plane 31 is projected onto a specially preparedhologram 32, using a standard projection lens 33. The hologram is sodesigned that when illuminated with such a reference beam, it willgenerate an object beam which when projected through a second projectionlens 34, will image onto another plane a picture having the verticalrows arranged side-by-side horizontally 35. The hologram used here issimilar to the second hologram, 21, in FIG. 4. (It is highly desirableto replace the projection lenses by two matrix lens arrays as is shownin FIG. 3. This is also illustrated as the first hologram, 20, in FIG.4.) The method to fabricate such a hologram can be illustrated usingFIG. 6. Replace the secondary and unscrambled image planes (31 and 35respectively) by diffusing screens. Apertures must be used with bothreference and object beams so as to direct the location, size and shapeof each corresponding row between the secondary and unscrambled imageplanes. This holographic imaging device is then fabricated by the samemethod as that which is shown in FIG. 5 as previously described. (Thisis not to say that the holographic imaging device described here is thesame as previously described and illustrated in FIG. 5, but only that itis fabricated in a similar manner.) Similarly, as with the previousholographic imaging device, an aperture could be used with thephotographic plate to solve the problem of emulsion reciprocity, or theshort-burst method can be used.

[0044] The method of inverting a pseudoscopic image is to reconstructthe 3-dimensional image in the usual manner and then to re-photographthe reconstruction with a second camera. The reconstruction of thissecond film will produce a pseudoscopic image of the 3-dimensional imagewhich was photographed. Since, this image was originally pseudoscopic,the pseudoscopic reconstruction of this image would be orthoscopic. Thismethod of image inversion is shown in FIG. 7. This technique has twomajor disadvantages. First, an intermediate processing step is requiredin which a second film must be made; second, there is an inherentresolution loss of {square root}{square root over (2)} when going fromone film to the other.

[0045] There is another basic method of producing orthoscopic imagesfrom pseudoscopic images which will not incur this resolution loss. Thismethod was described in patent '562. The basic principle is quitesimple. Referring to FIG. 8, if the film format shown in FIG. 8(a)produces a pseudoscopic image, then it can be shown by an opticalanalysis of what a second film record would look like were the3-dimensional image from FIG. 8(a) to be photographed, that the filmformat of FIG. 8(b) would produce an orthoscopic mirror image of thepseudoscopic 3-dimensional image produced by the format of FIG. 8(a),while format of FIG. 8(c) will produce a correct orthoscopic image.

[0046] The method for image inversion discussed here concerns itselfonly with its performance in the projector. Any intermediate processingwhere another film must be prepared is discussed in patent '562 only.The proposed method is to perform this inversion during unmultiplexingwhen a holographic imaging device is used (refer to FIG. 3). In thiscase, each element would be mirror image inverted, but the order of theelements could be kept in-tact holographically. In fact, the elementscan be holographically arranged in any order that is desired.

[0047] Accordingly, any of the holographic optical elements describedabove can be fabricated in a manner so that when an integralphotographic image is processed by it, the 3-dimensional image projectedtherefrom will be orthoscopic. This is done by optically reversing eachelemental image of the integral photograph separately as shown in FIG.8. When preparing the elemental parts of the holographic imaging device,the optics for elemental image inversion must be included.

[0048] Therefore, the schematic shown in FIG. 4, either including or notincluding the second matrix lens array 19, represents the ideal opticalsystem for projection and magnification of integral photographs. Notonly do the holograms cause projection and magnification of the integralphotographs on the screen, but they also unmultiplex the unmagnifiedintegral photograph and perform the appropriate image inversion requiredfor ultimate viewing of the resultant 3-dimensional scene.

[0049] Now turning to the issue of image multiplexing, patent '562describes one embodiment of the camera design that uses holographicoptics to accomplish the image dissection and multiplexing. This isshown conceptually in FIG. 9. In this case, reflection holograms areused because of their high diffraction efficiency (95-100%), althoughthe process would work conceptually even with transmission holograms.(The diagrams, however, are shown using reflection holograms.) Thisprocess involves the transfer of images from one holographic plane toanother plane with 1:1 magnification. (Several methods exist to provideabberation free magnification using holography, should this bedesirable.) In the figure, the image 36 is projected through the cameramatrix lens array 37 or otherwise focused onto hologram plane 38 which,in turn, projects the appropriate multiplexed frame onto the film, 39,using intermediate holographic planes (shown symbolically as planes 40)if necessary. These intermediate planes serve the purpose of allowingthe image to impinge onto the film from a far less severe angle, therebydecreasing the abberations. But, these intermediate planes may not benecessary. FIG. 10 shows conceptually how such a holographic plane canbe made. For clarity, multiplexing will be accomplished, in this figure,for only two rows. The image on the left with two rows, 41 and 42,arranged horizontally is projected using lens 43 onto hologram 44. Thisprojected image acts as a reference beam for the hologram, therefore,reconstructing an object beam which focuses an image in space 45,consisting of rows 41 and 42 arranged vertically. The hologram isprepared by using two moving apertures. The hologram is prepared usingeach elemental image of the primary integral photograph as the referencebeam and the corresponding elemental image of the secondary integralphotograph as the object beam and by exposing the photographic platewith both reference and object beams on opposite sides. The aperturesthen move to each pair of elemental images in turn, with the hologrambeing re-exposed each time. It could be desirable to use a third movingaperture and fourth moving aperture positioned adjacent to but onopposite sides of the photographic plate. Furthermore, it could bedesirable to use coherent light from a short burst laser to expose thephotographic plate so as to reduce noise.

[0050] The preferred embodiment of the screen is an array of cylindricalzone plates with associated color filtration. Zone plates can beproduced holographically. However, instead of being produced astransmission holograms, they are produced as reflection holograms.Reflection holograms are commonly manufactured by a process calledBragg-Angle Holography. In this instance, instead of the diffractionpattern being formed on the surface of the photographic emulsion whichmakes up the hologram, the diffraction pattern is formed in the volumeof the emulsion itself. Such a holographic zone plate would have thefollowing advantages:

[0051] (1) Since it is formed as a reflection hologram, this type ofscreen is applicable to front projection, the technique now in use inmost theaters.

[0052] (2) A reflection holographic screen accepts white light emanatingfrom a point source and reflects it into the audience at the wavelengthwith which the hologram was initially made. Since the zone plate screenconsists of a mosaic of alternating zone plates, each one produced as ahologram by laser light having a different wavelength, it becomesobvious that a holographic screen of this type already has its own colorplate “built-in”. Separate color filters are not required.

[0053] The screen is a Bragg Angle Reflection Hologram, which whenilluminated from the front with a beam of white light having a sphericalwavefront, the reconstruction will be a series of thin vertical lines,each line a different color, the colors alternating between red, greenand blue, each line projected in front of the screen a distance ƒ, andthe vertical lines will be arranged horizontally across the width of thescreen. A Bragg Angle Hologram is really a diffraction grating whosediffracting elements are distributed throughout the volume of theemulsion. A reconstruction can only be obtained by a reference beam ofthe same wavelength as was used to make the hologram. For thiswavelength, the reconstruction efficiency is extremely high. If a whitelight reference beam should be used, only the appropriate colorcomponent will be selected to perform the reconstruction.

[0054]FIG. 11(a) shows the fabrication of a reflection hologram withmonochromatic light. The reference beam is a spherical wavefront and thereconstruction is a real image of a single vertical line projected infront of the hologram. The object beam is created by passing a laserbeam 46 through a cylindrical lens 47 which focuses through a slit 48positioned at a distance ƒ from the photographic plate 49. The referencebeam is produced as a spherical wavefront from the same laser 46, and ismade to impinge upon the opposite side of the photographic plate 49.This operation can be performed separately for each wavelength needed,or the hologram can be fabricated as shown in FIG. 11(b). A white light,or multi-wavelength laser 50, such as a krypton laser, is used. Thecomplete beam having all color components is used as the reference beam54. The laser beam is split in two using a beam splitter 51 into twocomponents 52 and 53. Beam 52 ultimately becomes the reference beam 54after passing the optical components (mirrors M₁, M₂ and M₃, and concavelens L₁ and circular aperture S₁). Beam 53 ultimately becomes the objectbeams. First, the color components are separated by a prism 55. Theunwanted wavelength components are removed by mirrors MO and M₃ leavingonly the three red 56, green 57 and blue 58 object beams to be used tocreate the hologram. (Of course, colors other than red, green and bluecan be used as long as they are complementary colors which are used toform white.) Thus far only three zone plates have been created on thephotographic plate 59. The photographic plate 59 is then moved, and anew section is exposed in exactly the same manner. The method ofreconstruction is shown in FIG. 12. A white light reference beam with aspherical wavefront is used to reconstruct alternating red, green andblue cylindrical wavefronts. Should the reference beam emanate from aprojector in the rear of the theater with the image of an integralphotograph impressed on the beam such that the image of the integralphotograph is focused onto the screen, then a 3-dimensional image willbe reconstructed from the integral photograph. In this case, a colorfilter is not required, as the image will be properly broken down intothe appropriate color pattern, and black & white film must be used.

[0055] The screen need not be prepared as an extremely large hologram,as this would be impractical. Even in a very small theater, the screensize might be 20 feet wide×10 feet high. The mechanics of producing ahologram that large is formidable. Instead, smaller rectangular shapedtiles can be produced which are all identical. These tiles can then beassembled to produce a screen of any size.

[0056] Now we turn to the fabrication of high quality holographicimaging optics. With any ordinary optical system, when projecting a2-dimensional image, the projected image is normally degraded withrespect to the original image. This is true even at 1:1 magnification.The reason for this is that most optical systems exhibit inherentabberation and distortion. However, it is often required that aprojected image have extremely high quality with minimum abberation anddistortion. To accomplish this, special high quality optical systemsmust be used. Often such optics do not exist, and must be speciallydesigned and fabricated. Obtaining such optics can be very expensive.

[0057] Patent '562 discloses the requirement that projected images mustbe of extremely high quality, particularly during intermediateprocessing and intermediate projection. A special case of thisintermediate projection is when it is performed at no magnification.This is very useful in certain of the final projection systems discussedin patent '562. What is required is that an image be transferred fromone image plane to another at 1:1 magnification with the resolutionpreserved, i.e., the total information must be transferred from oneimage to the other. Such an imaging system is typically used for amicroprojector and semiconductor circuits. One such system was designedby PERKIN-ELMER several years ago. This optical system uses mirrorsinstead of lenses. It covers a field of two-inches. Resolution wasone-micron or 500 line pairs/mm. Of course such an optical system couldbe constructed using lenses, but it would be more complex and very muchmore expensive.

[0058] Holographic optics can be used to accomplish this type of highquality image transfer or projection. Reflection holography shoulddefinitely be used since the diffraction efficiency is much higher thanfor transmission holography. FIG. 13 shows how a non-permanent image canbe projected using the principle of primary holographic projection. The2-dimensional image from the film 60 is projected onto a reflectionhologram 61 using a 1:1 imaging optical system 62. The image is thenfocused onto a secondary image plane 63. In this case, a speciallydesigned abberation free lens 64 is used in conjunction with thehologram for projection. Since this expensive lens must be used duringnormal projection of the film, this method is not very practical.However, since a hologram is an imaging device itself, the hologram canbe used as a high quality lens.

[0059]FIG. 14 shows one method of fabricating such a hologram. The film60 of FIG. 13 is replaced by a translucent diffusing screen, and anothertranslucent diffusing screen is made to coincide with the secondaryimage plane 63 of FIG. 13. In this case the photographic plate istotally reflective on the side opposite from the emulsion. Bothdiffusing screens are trans-illuminated by the same laser and thehologram is exposed. The reference beam passes through the standard lenswhile the object beam passes through the high quality lens. Of course,this can also be accomplished by eliminating the reflective coating onthe reverse side of the photographic plate by causing the object beam toimpinge upon the reverse side of the plate. However, the efficiency ofthe reflective method is considerably higher.

[0060]FIG. 15 illustrates how such a hologram would be used. A standardprojection lens 65 images the film frame 66 onto the specially preparedhologram 67, which, in turn, acts as a reflecting lens to image the filmframe onto the secondary image plane 68 at some greater magnification.This hologram is a high quality Leith Hologram, and is indicatedoperating as a reflection hologram because the diffraction efficiency ismuch higher for reflection than for transmission.

[0061] The discussion now proceeds to holography of a 2-dimensionalintegral photographic film. In this method a holographic movie film isused. However, the projected real image of the hologram is a2-dimensional image which is projected onto a diffusing screen (orimaginary image plane). This image is the integral photograph to beprojected. This process is illustrated in FIG. 16. Since the initialphotograph that will be taken by the camera is an integral photograph, ahologram can be taken of each frame of the integral photographic film,and the reconstructed image will, therefore, be the integral photograph.Referring to FIG. 16, to construct the hologram 69, a laser beam 70passing through a standard projection lens 71 serves as the referencebeam. The integral photographic frame is projected using the same laserbeam onto diffusing screen 73 which produces the object beam 74. Thecombination of reference beam 72 and object beam 74 produces thehologram. To reverse the process for projection, light impinges uponprojection lens 71 and then upon the holographic film frame 69. Thisreconstructs object beam 74 that produces a focused image of theintegral photograph on diffusing screen 73. This method contrasts withthat of direct holography where holograms are taken of the scenedirectly.

[0062] In 1968, Dr. D. J. DeBitetto of Phillips Laboratories, BriarcliffManor, N.Y., published several articles concerning holographic3-dimensional movies with constant velocity film transport. In thesearticles, he described holograms produced which allowed bandwidthreduction by elimination of vertical parallax. This was accomplished bymaking the 3-dimensional holograms on a film strip using a horizontalslit as an aperture. The frames were formed by advancing the film eachtime by the width of the slit. Each frame was animated. Afterdevelopment, the film was illuminated as any hologram would be, and thefilmstrip was moved at constant velocity. I have seen Dr. DeBitetto'sholographic movies, and they are the best attempts to-date in the fieldof motion picture holography. The 3-dimensional pictures are ofextremely high quality. However, vertical parallax was absent.

[0063] The same technique can be used in our projector. It can be usedwith direct holography as Dr. DeBitetto did or it can be used withholograms of integral photographs as shown in FIG. 17. In this figure,and by this technique, a horizontal strip hologram 75 is taken of eachintegral photographic frame 76 (in any format, multiplexed orunmultiplexed), and the holographic film strip is advanced for eachframe. This is done by projecting the integral photographic frame 76onto a diffuser plate 77 using coherent illumination from a multicolorlaser 78 (e.g., a white light krypton laser). This becomes the objectbeam necessary to produce the hologram. It is possible to take severalstrip holograms of the same frame. Afterwards, the holographic film 79is played back in the projector at constant velocity.

[0064] Dr. DeBitetto takes his holograms as strip holograms in that boththe holography and projection must be performed with the slit aperture.This requires the holography of a very large number of small stripframes, the animation of each frame showing only slight or minusculemotion with respect to the previous frame. This is contrasted with themethod of taking holographic movies where each frame has a reasonablesize both in height and in width (as would be expected in a standardformat motion picture film). Obviously, Dr. DeBitetto's technique hasthe disadvantage of requiring an extremely large number of frames, thusmaking the process very arduous. However, this patent applicationsubmits that the frames be prepared in the standard motion pictureformat (as opposed to horizontal strip holograms), and that the frame beprojected with a horizontal slit aperture. The film is used in the sameway as in Dr. DeBitefto's process, and is projected at constantvelocity. The image projected from the hologram onto the screen willonly change in vertical parallax as the frame moves by the aperture.However if the film format used is that previously described forholography of the original 2-dimensional integral photographic film,then the vertical parallax does not change as the frame moves by,because the projected image is 2-dimensional and has no vertical (norhorizontal) parallax. The image only changes, therefore, when a newframe comes into view. Therefore, the height of the frame required forthe holographic film will depend upon the film velocity and the framerate. This represents the preferred embodiment for the holographicprojector.

[0065] Constant velocity is a tremendous advantage for projection of3-dimensional movies. Since film registration must be held to extremelytight tolerances, not having to stop the film for each frame wouldprovide much needed stability, and film registration would be farsimpler. Without this constant velocity transport, each frame would haveto be registered with the three-point registration system as describedin patent '562. Furthermore, constant velocity film transport reducesthe probability of film breakage.

[0066] The discussion now turns to intermediate processing of the film.In the previous discussions of the formation of orthoscopic images frompseudoscopic images, image inversion was accomplished during theprojection stage. It is considered more desirable to accomplish thisoperation during the projection stage because it can be done without theinherent loss in resolution (a factor of {square root}{square root over(2)}) attached to a process in which a new integral photograph orhologram must be copied from the 3-dimensional projected image. Shouldit be desired to make a film to be presented to motion picture theaters,which, in turn, when projected, would produce orthoscopic images, thenthe best method of making such films from the original would be by theprojection techniques previously discussed. These projection techniquescan be used for film copying as well as for projection onto a screen.However, for the sake of completeness of this application, the methodsfor image inversion, by making a new integral photograph or hologramfrom the original reconstructed 3-dimensional pseudoscopic image, willbe presented.

[0067]FIGS. 18, 19 and 20 show how to perform this inversion. FIG. 18illustrates converting from one integral photograph to another; FIG. 19,from an integral photograph to a hologram; and FIG. 20, from onehologram to another. Note that, in each of these setups the film uponwhich the new integral photograph or hologram is to be produced may bepositioned anywhere with respect to the pseudoscopic image. What isimportant is that the original reconstructed wavefronts be used to formthe new record and not the image.

What is claimed is:
 1. A method of preparing a hologram to be used in asystem for recording and projection of images in substantially3-dimensional format, said method comprising the steps of: producing thereference beam by passing diffuse coherent light from a laser through afirst active optical system containing a plurality of image focusingmeans therein; and producing the object beam by passing diffuse coherentlight from the same laser through a second active optical systemcontaining a plurality of image focusing means therein of the samenumber and arrangement as the first active optical system, the F-numberof each said focusing means of the second active optical system beingthe same as the F-number of the first active optical system, and eachsaid focusing means of the first optical system, wherein all of thecomponent parts of an equation used for determining the F-number of thesecond optical system are substantially the same multiples of all of thecomponent parts used for determining the F-number of the first activeoptical system, respectively, said multiple being equal to the expectedmagnification of the 3-dimensional image.
 2. A method according to claim1 wherein a movable aperture is made a part of each of said two activeoptical systems such that the size and shape of the aperture of thefirst active optical system is the same as an elemental image of theunmagnified integral photograph and the size and shape of said apertureof the second active optical system is the same as an elemental image ofthe magnified integral photograph, said movable aperture being placedbetween the diffuser plate and each of the image focusing meanscontained in the active optical system and adjacent to the surface ofthe diffuser plate, and said method comprising the steps of: positioningsaid movable aperture in the first active optical system so that itcoincides with the position of the first elemental image of theunmagnified integral photograph; and, positioning said movable aperturein the second active optical system so that it coincides with theposition of the first elemental image of the magnified integralphotograph; and, producing the reference beam by passing diffusecoherent light from a laser through the first active optical system;and, producing the object beam by passing diffuse coherent light fromthe same laser through the second active optical system; and, allowingthe reference and object beams to impinge upon the photographic platefor a sufficient time to expose the hologram; and, thereafter,positioning said movable aperture in the first active optical system sothat it coincides with the positions of the second elemental image ofthe unmagnified integral photograph, the third elemental image of theunmagnified integral photograph, the fourth elemental image of theunmagnified integral photograph, and so on, each positioning of theaperture comprising a step in the process; and, at the same time,positioning said movable aperture in the second active optical system sothat it coincides with the positions of the second elemental image ofthe magnified integral photograph, the third elemental image of themagnified integral photograph, the fourth elemental image of themagnified integral photograph, and so on, each positioning of saidaperture comprising a corresponding simultaneous step in the process;and, for each corresponding step, produce the reference and object beamsand in the same manner as they were produced for the first elementalposition; and, for each corresponding step, expose the same hologram inthe same manner as it was in the previous steps, making sure that bothapertures always move together.
 3. A method according to claim 2 whereinshort bursts of low intensity laser radiation are used as the source ofcoherent light for exposure of the hologram.
 4. A method according toclaim 2 wherein a third movable aperture is placed in contact with theemulsion of the photographic plate that is to become the hologram andwherein a fourth movable aperture is placed on the opposite side of thephotographic plate that is to become the hologram, so that the both thethird and fourth apertures are always positioned coincidentally so as topermit the maximum amount of light to pass through the photographicplate, and wherein the third and fourth apertures move together with thefirst and second apertures in such a manner as to only expose an elementof the hologram, said elemental position corresponding with thepositions of the first and second apertures that also always movetogether.
 5. A method according to claim 2 wherein optics to produce amirror image of each of the elemental images of the integral photographto be magnified is used in preparing the hologram so that when themagnified integral photograph is produced each elemental image of themagnified integral photograph is the mirror image of its correspondingelemental image of the unmagnified integral photograph but the spatialarrangement of the elemental images of both the unmagnified andmagnified integral photographs is the same.
 6. A method according toclaim 5 wherein the magnification factor is unity.
 7. A method accordingto claim 5 wherein optics to produce the elemental images of theintegral photograph to be magnified is used in preparing the hologram sothat when the magnified integral photograph is produced each elementalimage of the magnified integral photograph is the same as itscorresponding elemental image of the unmagnified integral photograph butthe spatial arrangement of the elemental images of magnified integralphotograph is reversed with respect to the corresponding elementalimages of the unmagnified integral photograph.
 8. A method according toclaim 7 wherein the magnification factor is unity.
 9. A method ofpreparing a hologram to be used for elemental image multiplexing in asystem for recording and projection of images in substantially3-dimensional format, said method comprising the steps of: positioning afirst movable aperture in the unmultiplexed image plane so that itcoincides with the position of the first elemental image of theunmultiplexed integral photograph; and, positioning a second movableaperture in the multiplexed image plane so that it coincides with theposition of the first elemental image of the multiplexed integralphotograph; and, producing the reference beam by passing diffusecoherent light from a laser through the first aperture; and, producingthe object beam by passing diffuse coherent light from the same laserthrough a second aperture; and, allowing the reference and object beamsto impinge upon the photographic plate for a sufficient time to exposethe hologram; and, thereafter, positioning the first movable aperture inthe unmultiplexed image plane so that it coincides with the positions ofthe second elemental image of the unmultiplexed integral photograph, thethird elemental image of the unmultiplexed integral photograph, thefourth elemental image of the unmultiplexed integral photograph, and soon, each positioning of the aperture comprising a step in the process;and, at the same time, positioning the second movable aperture in themultiplexed image plane so that it coincides with the positions of thesecond elemental image of the multiplexed integral photograph, the thirdelemental image of the multiplexed integral photograph, the fourthelemental image of the multiplexed integral photograph, and so on, eachpositioning of the aperture comprising a corresponding simultaneous stepin the process; and, for each corresponding step, produce the referenceand object beams and in the same manner as they were produced for thefirst elemental position; and, for each corresponding step, expose thesame hologram in the same manner as it was in the previous steps, makingsure that both apertures always move together.
 10. A method according toclaim 9 wherein short bursts of low intensity laser radiation are usedas the source of coherent light for exposure of the hologram.
 11. Amethod according to claim 9 wherein a third movable aperture is placedin contact with the emulsion of said photographic plate and wherein afourth movable aperture is placed on the opposite side of saidphotographic plate, so that the both the third and fourth apertures arealways positioned coincidentally so as to permit the maximum amount oflight to pass through the photographic plate, and wherein the third andfourth apertures move together with the first and second apertures insuch a manner as to only expose an element of the hologram.
 12. A methodof preparing a hologram to be used as a front projection holographicscreen for reconstructing magnified 3-dimensional images projected fromunmagnified integral photographs or holograms, wherein at least threemonochromatic laser beams are used to prepare the hologram, such thatthe three wavelengths of laser light are complementary so as to producethe appearance of white light, said method comprising the steps of:optically splitting the first monochromatic laser beam into a referencebeam and an object beam such that the reference beam has a sphericalwavefront that appears to have been generated at a reasonably largedistance and the object beam has a cylindrical wavefront that appears tohave been generated at a calculated distance (a focal point for thatwavelength); and, exposing a transparent photographic plate with saidmonochromatic laser light such that the reference beam impinges on theemulsion side of the photographic plate while the object beam impingeson the side opposite from the emulsion, in such a manner wherein thereference beam exposes the entire plane of the photographic plate in alldirections, and the object beam results from a line of light thatextends across the entire photographic plate in the linear dimension anda distance ƒ from the surface of the emulsion, said distance ƒ beingcalculated as the focal length from the required (F/#) of the screenfocusing elements; and, repeating the previous two steps for the secondmonochromatic laser beam such that the line of light exposed by theobject beam is adjacent to and parallel to the line of light exposed bythe first monochromatic laser, such that the two lines are notcoincident; and, repeating the first two steps for the thirdmonochromatic laser beam such that the line of light exposed by theobject beam is adjacent to and parallel to the line of light exposed bythe second monochromatic laser, such that it is not coincident with theline produced by either the first or second monochromatic laser; and,repeating all of the above steps to ultimately form a number of paralleladjacent sets of three adjacent parallel lines produced by the threemonochromatic laser beams so that they may repeat in groups of threeacross the entire photographic plate.
 13. A method according to claim 12wherein the reference and object beams both impinge on the emulsion sideof the photographic plate.
 14. A method according to claim 13 whereinthe side of the photographic plate opposite from the emulsion isnon-transparent and reflective.
 15. A method according to claim 12wherein the object beams are repositioned optically between successiveexposures of the photographic plate so as to produce parallel lines. 16.A method according to claim 12 wherein the photographic plate isrepositioned mechanically between successive exposures of thephotographic plate so as to produce parallel lines.
 17. A methodaccording to claim 12 wherein the wavelengths of the three monochromaticlaser beams can be roughly characterized as red, blue and green,respectively.
 18. A method according to claim 12 wherein the wavelengthsof the three monochromatic laser beams are all components of a singlelaser capable of producing white coherent laser light.
 19. A methodaccording to claim 18 wherein the laser used is a krypton laser.
 20. Amethod according to claim 18 wherein the reference beam is a sphericalwavefront comprised of several or all of the wavelengths produced by thewhite light laser.
 21. A method according to claim 12 wherein thedistance that each real image of the line of light used in the objectbeam is from the photographic emulsion is computed based upon the focallength required for the particular wavelength of monochromatic lightused to produce its portion of the hologram.
 22. A method according toclaim 12 wherein the holograms are produced as identical rectangulartiles, and the theater screen is produced by assembling the tiles.
 23. Amethod of preparing a hologram to be used in a system for recording andprojection of images in substantially 3-dimensional format as a highquality holographic imaging system to transfer low abberation and lowdistortion images, said method comprising the steps of: passing coherentlight emanating from a laser through a first diffusing screen andfurther passing the resulting scattered coherent light through astandard projection lens that neither magnifies nor demagnifies, whereinthe resulting coherent light becomes the reference beam; and, passingcoherent light emanating from the same laser through a second diffusingscreen and further passing the resulting scattered coherent lightthrough a high quality lens system specially designed to be abberationand distortion free, wherein the resulting coherent light becomes theobject beam; and, exposing the a photographic plate with both referenceand object beams to produce the hologram.
 24. A method according toclaim 23 wherein the reference and object beam impinge upon oppositesides of a transparent photographic plate to expose the hologram.
 25. Amethod according to claim 23 wherein the reference and object beamimpinge upon the same side of a photographic plate to expose thehologram.
 26. A method according to claim 25 wherein the reference andobject beam impinge upon the emulsion side of a photographic plate toexpose the hologram.
 27. A method according to claim 26 wherein the sideof the photographic plate that is opposite to the emulsion is anon-transparent reflective surface.
 28. A method according to claim 23wherein the hologram is produced as a reflection hologram.
 29. A methodaccording to claim 23 wherein the hologram is produced as a transmissionhologram.
 30. A method of making a hologram capable of reconstructing animage in substantially 3-dimensional format when used with an activeoptical system containing a plurality of image focusing means therein,said method comprising the steps of: passing a laser beam through astandard lens so as to produce the reference beam; and, illuminating anintegral photograph using the same laser; and, projecting said laserilluminated image of the integral photograph onto a diffuser plate so asto produce the object beam; and, allowing the laser and object beams topass through an aperture or slit, and impinge together upon the surfaceof a photographic film or plate for a sufficient time for photographicexposure.
 31. A method of making a holographic film strip to be used ina system for recording and projection of images in substantially3-dimensional format, according to claim 30 , wherein said film stripconsists of successive holograms each hologram being capable ofreconstructing a 2-dimensional real image of an integral photograph. 32.A method of making a holographic film strip according to claim 31wherein the object beam is formed from the image of an integralphotograph, such that the 3-dimensional image that would have beenproduced by reconstruction of said integral photograph has no verticalparallax, thereby permitting said holographic film strip to be advancedthrough a projector at constant velocity.
 33. A method of preparing asecond integral photograph to be used in a system for recording andprojection of images in substantially 3-dimensional format, from a firstintegral photograph wherein said first integral photograph used togetherwith an active optical system consisting of a plurality of imagefocusing means therein reconstructs a 3-dimensional image that ispseudoscopic, and wherein said second integral photograph used togetherwith an active optical system consisting of a plurality of imagefocusing means therein reconstructs a 3-dimensional image that isorthoscopic, said method comprising the steps of: reconstructing apseudoscopic real image from the first integral photograph using anactive optical system consisting of a plurality of image focusing meanstherein; and, photographing the pseudoscopic real image onto aphotographic film or plate using an identical active optical systemconsisting of a plurality of image focusing means therein as was used toreconstruct the pseudoscopic real image from said first integralphotograph.
 34. A method of preparing a hologram to be used in a systemfor recording and projection of images in substantially 3-dimensionalformat, from an integral photograph wherein said integral photographused together with an active optical system consisting of a plurality ofimage focusing means therein reconstructs a 3-dimensional image that ispseudoscopic, and wherein said hologram reconstructs a 3-dimensionalimage that is orthoscopic, said method comprising the steps of:illuminating the integral photograph with coherent radiation from alaser, thereby producing an object beam by reconstructing a pseudoscopicreal image from said integral photograph using an active optical systemconsisting of a plurality of image focusing means therein; and,producing a reference beam using the same laser as was used toilluminate the integral photograph; and exposing a photographic plate orfilm using the reference and object beams so produced.
 35. A method ofpreparing a second hologram to be used in a system for recording andprojection of images in substantially 3-dimensional format, from a firsthologram wherein said first hologram reconstructs a 3-dimensional imagethat is pseudoscopic, and wherein said second hologram reconstructs a3-dimensional image that is orthoscopic, said method comprising thesteps of: illuminating said first hologram with coherent radiation froma laser, thereby producing an object beam by reconstructing apseudoscopic real image; and, producing a reference beam from the samelaser as was used to illuminate said first hologram; and exposing aphotographic plate or film using the reference and object beams soproduced.